Security researchers have found flaws in four popular connected storage drives that they say could let hackers access a user’s private and sensitive data.

The researchers Paulos Yibelo and Daniel Eshetu said the software running on three of the devices they tested — NetGear Stora, Seagate Home, and Medion LifeCloud — can allow an attacker to remotely read, change and delete data without requiring a password.

Yibelo, who shared the research with TechCrunch this week and posted the findings Friday, said that many other devices may be at risk.

The software, Hipserv, built by tech company Axentra, was largely to blame for three of the four flaws they found. Hipserv is Linux-based, and uses several web technologies — including PHP — to power the web interface. But the researchers found that bugs could let them read files on the drive without any authentication. It also meant they could run any command they wanted as “root” — the built-in user account with the highest level of access — making the data on the device vulnerable to prying eyes or destruction.

We contacted Axentra for comment on Thursday but did not hear back by the time of writing.

Neither Netgear nor Seagate commented by our deadline, but we’ll update if that changes. Lenovo, which now owns Medion, did not respond to a request for comment.

The researchers also reported a separate bug affecting WD My Book Live drives, which can allow an attacker to remotely gain root access.

A spokesperson for WD said that the vulnerability report affects devices originally introduced in 2010 and discontinued in 2014, and “no longer covered under our device software support lifecycle.” WD added: “We encourage users who wish to continue operating these legacy products to configure their firewall to prevent remote access to these devices, and to take measures to ensure that only trusted devices on the local network have access to the device.”

In all four vulnerabilities, the researchers said that an attacker only needs to know the IP address of an affected drive. That isn’t so difficult in this day and age, thanks to sites like Shodan, a search engine for publicly available devices and databases, and similar search and indexing services.

Depending on where you look, the number of affected devices varies. Shodan puts the number at 311,705, but ZoomEye puts the figure at closer to 1.8 million devices.

Although the researchers described the bugs in moderate detail, they said they have no plans to release any exploit code to prevent attackers taking advantage of the flaws.

Their advice: if you’re running a cloud drive, “make sure to remove your device from the internet.”